Based on the striking similarity of the age distributions of infant botulism and the Sudden Infant Death Syndrome (SIDS); on the clinical spectrum of infant botulism that includes cases considered typical SIDS; and on the now accepted pathogenesis of infant botulism, we believe that infant botulism may be the prototype of a class of diseases caused by various toxin-producing clostridia that colonize the infant gut and whose toxins are capable of causing SIDS. The long-term objective of this research is to elucidate the epidemiology of infant botulism, identify associated host and environmental risk factors, and to use this knowledge to design preventive measures applicable to infant botulism and other "toxigenic intestinal infections of infancy." Specific Aims: 1. To determine the epidemiology of infant botulism by means of a case-control epidemiological and laboratory study. 2. To identify those factors that determine the clinical severity of disease, i.e., why the paralysis of infant botulism begins gradually in some infants, while in others it occurs rapidly and produces sudden, unexpected death that is autopsy is indistinguishable from typical crib death (sudden infant death syndrome, SIDS). 3. To develop a profile of the infant at high risk of infant botulism. 4. To utilize the study populations built up in the first three years of this grant (i.e., cooperative lactating mothers and their infants) to further investigate the physiological basis of our epidemiological observation that human milk offers protection against suddent death from infant botulism. 5. To use our case and control infant populations to investigate the possible role that other toxin-producing clostridia (e.g., C. difficile, C. perfringens) may play as unrecognized causes of infant morbidity and mortality.